Tiagra Triple problems. HELP!

I have had my tandem for a little while now and have not been impressed by the performance of my drivetrain, was wondering if it is what I should expect or if there is anything I can do to improve it. Slower shifting I can imagine being a problem as there is more friction on the cables/longer cables, but these problems I don't know that they are tandem specific. Front derailler is a Tiagra triple, SRAM X7 Grip shifters. Problems have included dropped chains (even when not climbing or pedaling hard), FD rubbing on chainring, chain rub when even a little bit cross chained (middle ring, small cog; small ring, 3rd cog, etc). Initially wasn't shifting into small ring. I played around extensively, and couldn't get things much better. Took it back to the shop to be re-adjusted, and was told that was the best I could expect. Currently in order to reach small chain ring FD is set up at a slight angle, however this means that unless the chainline isn't perfectly straight or nearly so, the chain rubs on the FD. Also the FD/shifter is set up so that I have no trim and it doesn't use the full range of pull. I have owned a several single road bikes (a 105, and a Campy Veloce in triple and a DA, and some older Shimano double) in the past and never had these issues, also never had these problems with a MTB. Is this what I can expect with this setup? Should I upgrade? Is there a trick to adjusting this properly that me and the pro mechanic are missing? Going to a double is not an option as I haul a lot of crap, plus my two kids around on a routine basis, but I am willing to upgrade to Ultegra or even DA, or slap all XT or comparable SRAM on if needed (stock riser bar in front which I like right now as I am getting used to the tandem, and I can muscle it around if I need to). HELP!

First, get yourself a jump stop. That will keep the chain from dropping off the small chainring.
I don't care how well the derailleur is adjusted and how good you are at shifting the chain is coming off at some point (like Andy Schleck)
I use this one but there are others depending on what fits your bike:

I have one on all bikes including singles with double rings and chain NEVER comes off the small ring.

In general I thought Shimano stuff at different levels all worked about the same, Dura Ace, Ultegra or whatever.
Not sure if Tiagra does not shift as well.
I have had good luck with Shimano XTR and Campy Comp Triple.
The problem could also be the chain rings if they do not have good ramps and pins.
I try to mount the FD parallel to the chain rings, having it at an angle is not a good idea.
Also check that the derailleur is not mounted too high above the chain rings, there should be about 2mm clearance to the big chain ring.
Chain width is also going to be a factor. Using a narrow chain with a derailleur that has a wide cage or visa versa may be problematic.
In general you want all the drive train components to be matched for how many speeds you have 8, 9 or 10.

In general I thought Shimano stuff at different levels all worked about the same, Dura Ace, Ultegra or whatever.
Not sure if Tiagra does not shift as well.
I have had good luck with Shimano XTR and Campy Comp Triple.
The problem could also be the chain rings if they do not have good ramps and pins.
I try to mount the FD parallel to the chain rings, having it at an angle is not a good idea.
Also check that the derailleur is not mounted too high above the chain rings, there should be about 2mm clearance to the big chain ring.
Chain width is also going to be a factor. Using a narrow chain with a derailleur that has a wide cage or visa versa may be problematic.
In general you want all the drive train components to be matched for how many speeds you have 8, 9 or 10.

I too have heard that Shimano stuff was all pretty comparable as far as reliable shifting goes. I gotta say my DA was a bit crisper than my 105, but it was also newer (I liked the shifting of my Veloce equipped bike better than the Dura-Ace if that helps bring attention to this thread ) .
Regardign the problem at hand. I tried it parallel, and the rubbing was reduced, but I couldn't get it into the small ring. I will try lowering it a bit, but I did try it at various heights. Crankset is Ultegra. Chain looks like 9 speed, (everything else is 9 speed) I will check the model if I can find it on the chain. Does the wider spacing of the rear hub on a tandem make a difference setup? There aren't any spacers or anything between the frame and the cassette, and the spacing is 145mm, so the cassette is sitting a bit further over than it would be on a single...

We've got a tandem with Tiagra STI shifters, Tiagra FD and XT RD. I was worried when we bought it because all of our bikes always have had Ultegra or Dura-Ace stuff but the Tiagra works perfectly, really no difference to Ultegra. I was pleasantly surprised. We did have some troubles with the FD dropping chains but a Third Eye chain watcher solved that problem. We also needed to adujst the FD and chainge it's mounting position slightlyAs jnbrown mentions just be certain the FD is adjusted and set up perfectly. Our bike shop owner set up the FD with a very slight angle and it improved shifting after the adjustment.

I would compare the shape and width of the cage of your Tiagra FD to an Ultegra and/or Campy triple FD.
It could be the cage is not optimal for your setup.
Replacing the FD doesn't cost a whole lot so it might worth doing although not a guarantee to fix or improve the problem since you really don't have a diagnosis.

Sounds like a tuneing issue, I dont know how many tandems & single bikes I have repaired or tuned were bike shops and others have tried and tried at no end to tune or fix a problem just greating more issues. With that being said your situation may be special not seeing the tandem in person and knowing all the facts, condition of componets and tweaks maid. The componets should work fine if tuned right and set to spec accross the board. Tandems are a little more finicky and a little less forgiving than there single counterparts in the same configuration but if the parts are in spec and of proper condition all should work without tweaks like twisting the deraileur around and stuff like that. Good componets, good chain, proper tuning all should work.

Grip shifters only have three positions for the front Deraileur Low, Mid, and High. The Mid should allow you the use of all your rear cassette gears without scraping and relys on cable tension to hold this adjustment, to little it will scrape in the higher gears in the back on the middle ring up front, to much tension and it will scrape in the lower gears in the back on the middle ring up front. The Low or little ring up front should allow the use of 4 to 5 of your low cogs without an issue and the High ring or big ring up front should do the same on the other end of the spectrum. There should be enough adjustment on the front derailuer for the deraileur to be in the right position and allow several mm clearance in the small ring up front and the biggest cog in the back between the deraileur and the chain and the same goes for the big ring up front along with the smallest cog in the back ( there is a proper procedure for doing this adjustment on this type of set up with grip shifters, a lot of mountain bikes have this same issue only having 3 set points in the shifter Low, Middle and High or 1,2,3) There are other things to look at as well proper deraileur position is key along with low and high set points and proper cable tention as mentioned above.

Also as mentioned by others a properly set up Jump Stop is worth it's weight in Gold.